In order to prevent unauthorized copying of original printed documents, techniques which append specific image information such as background pattern when the original document is printed have been used. This specific image information is often referred to as “copy discouraging information” or “anti-copy information”.
For example, when image data is fed from an application running on a personal computer to a printer for printing out the image data from the printer, specific image information which discourages the copying of the image to be printed is fed to the printer together with the above image data, and embedded in somewhere of the image to be printed for printing out.
When trying to copy the printed image in which the specific image information is embedded, the copy machine which has detected the specific image information will not output the copied image or output a copy sheet having thereon characters such as “Copy Prohibited”.
The above-mentioned specific image information may be embedded in printed image in the way that it can not be recognized by the user or it can be recognized by the user that it is the specific image information.
In either case, the copy machine detects the presence of the specific image information in the image information when the image information in which the specific image information is embedded is copied and conducts predetermined processing such as prohibition of the copying per se or outputting of a copied image having characters “Copy Prohibited” in response to a detection result.
In connection with the technique for prohibiting unauthorized copying, a copy machine which is capable of easily making an original document bearing specific pattern thereon is disclosed in, for example, Japanese Laid-Open Patent Publication No. H7-38737. The copy machine comprises generating means for generating (a) specific mark(s) for reproducing the image with appending the specific mark(s) to an original document image; mark detecting means for detecting the presence of the specific mark(s) in read original document image; and control means which conducts the copying operation which is different from usual copying operation if the specific mark is detected in the original document image is detected by said mark detecting means.
A copy machine which reproduces an image which makes it possible to detect the specific mark(s) in an easy and precise manner is disclosed in Japanese Laid-Open Patent Publication No. H7-36325. This copy machine has a capability of reproducing an image to which (a) specific mark(s) is/are appended by mark appending means. The mark appending means appends specific marks, each comprising a plurality of concentric circles having different diameters, to the original document image.
In the above-mentioned system which embeds the specific image information in the printed image for printing out, the specific image information is always embedded in the printed image irrespective of the importance degree or secrecy of the image to be printed and the embedded image is printed out. Such a system has a problem in that the specific image information can not be positively detected in a copy machine if the original printed document has graffiti or if foreign materials or dirt is adhered to the specific image information in the original document. There occurs another problem in that if a number of items of the specific image information are appended at random on the printed image so that the copy machine can positively detect the presence of the specific image information, the specific image information will make the printed image worse in appearance or cause discomfort to a viewer viewing the image.
In other words, when printing image data on a recording material, in order to prevent copying of obtained image data or discourage copying per se, it is effective to append specific image information like the above to image data. On the other hand, appending specific image information like the above to usual printed matter which does not require discouraging of copying may give an adverse influence upon the appearance of the copied image.
In view of this point, no technical concept of changing the conditions of appending copying discouraging information depending upon image data is disclosed in both Japanese Laid-Open Patent Publications Nos. H7-38737 and H7-36325.